1. Field of the Invention
This invention pertains to the field of mechanical compression-type refrigeration which employs a condenser and evaporator, a volatile refrigerant and a compressor for withdrawing refrigerant vapor from the evaporator, raising its pressure and delivering it to the condenser for condensation. More specifically within that field, the invention relates to the area of suction line accumulators intended for installation in the suction conduit connecting the evaporator outlet and the compressor inlet. The purpose of these accumulators is the separation and retention of liquid refrigerant which from time to time might be delivered to it with the usual flow of refrigerant vapor from the evaporator, whether inadvertently by a malfunction of some control portion of the system, or intentionally.
2. Description of the Prior Art
The prior art discloses suction accumulators intended for location in the suction line of compression-type refrigeration systems intended for the interception and collection of liquid refrigerant and oil while at the same time allowing refrigerant vapor to flow unimpeded to the compressor. Even the simplest of these utilize some means for allowing the return of oil, circulated by the compressor with the refrigerant, such as an orifice port or metering tube so located as to drain the bottom of the accumulator tank and meter its contents into the outlet connection of the accumulator. These rudimentary accumulators of the prior art invariably had the characteristic that the metering assembly had sufficient flow capacity to return any reasonable quantity of the viscous oil circulated by the compressor. This same metering assembly, which had sufficient flow capacity to allow the return of the highly viscous oil, also had sufficient flow capacity to allow the flow of excessive quantities of the highly fluid liquid refrigerant under those conditions when the accumulator tank was partly filled with this refrigerant liquid. Up to the time of this invention, the prior art disclosed the following attempts to cope with this problem:
A. interchangeable metering tubes to allow the size metering tube to be finally selected which had the smallest inside diameter which could return the oil circulated by the system. PA1 B. various venturi devices whose incentive for liquid return increased with the refrigerant vapor flow rate but which could not differentiate between viscous oil and fluid refrigerant liquid. PA1 C. heated metering tubes to warm the oil, allowing it to become less viscous and flow more readily through a small metering tube, or to boil away the liquid refrigerant before it could reach the outlet connection of the accumulator; or to cause sufficient bubbling in the liquid refrigerant that its flow characteristics would become similar to that of the viscous oil and the flow rate of the bubbling, foaming, liquid refrigerant through the metering tube would be tolerably low.
Unfortunately, none of these improvements have been sufficiently satisfactory to allow free flow of the circulated oil and to control the flow of liquid refrigerant from the partially filled accumulator to such a value that it would not harm a close-connected compressor, whose temperature was as low as the temperature of the flowing, liquid refrigerant.